Compositions for the production of objects using additive manufacturing

ABSTRACT

This invention relates to an object comprised of a plurality of fused filaments of a polyester material that includes units of a diacid component and units of a glycol component. The co-polyester has a zero shear viscosity no greater than about 3000, an elongation at break of at least about 75%, a density no greater than about 1.25 g/cm3, a glass transition temperature of at least about 80° C., an inherent viscosity from about 0.55 dL/g to about 0.7 dig, a density no greater than about 1.25 g/cm3, and a crystallization half-time no greater than about 300 minutes.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.15/245,221, filed Aug. 24, 2016, which claims the benefit of U.S.Provisional Patent Application No. 62/215,950, filed Sep. 9, 2015, thecontents of which are incorporated herein by reference in theirentirety.

BACKGROUND

Additive manufacturing is a process used to produce three-dimensional(3D) objects. Additive manufacturing can be performed by extruding amaterial through a nozzle and depositing (typically layer-by-layer) thematerial onto a substrate to form an object. In some instances, thematerial used to form the layers of the 3D object may be referred toherein as “build material.” Extrusion-based additive manufacturing issometimes called “fused deposition Modeling®” (FDM®), which is atrademark of Stratasys Ltd. Of Edina, Minn., “fused filamentfabrication” (FFF), or more generally, “3D printing.”

Additive manufacturing processes often utilize electronic data thatrepresents an object, such as a computer-aided design (CAD) model of theobject, to form the object. The electronic data can be processed by acomputing device component of the additive manufacturing apparatus(e.g., a 3D printer) to form the object. For example, an electronicrepresentation of the object can be mathematically sliced into multiplehorizontal layers. The horizontal layers can have contours that willproduce the shape of the object being formed by the additivemanufacturing apparatus. The computing device component can generate abuild path to form the contours for each horizontal layer and sendcontrol signals to the extrusion portion of the additive manufacturingapparatus to move a nozzle along the build path to deposit an amount ofthe build material to form each of the horizontal layers. The horizontallayers are formed on top of each other by depositing fluent strands(also referred to as “roads”) of the build material in a layer-by-layermanner onto a platform or a build substrate. For example, the additivemanufacturing system can move an extrusion head, the build substrate, orboth the extrusion head and the build substrate vertically andhorizontally relative to each other to form the object. The buildmaterial from which the object is formed hardens shortly after extrusionto form a solid 3D object.

SUMMARY

The disclosure is directed to compositions for producing objects usingan additive manufacturing process. The compositions can be formed into afilament that is used in an additive manufacturing process to produce anobject.

An article can comprise a plurality of layers of a polymeric materialthat includes units of a diacid component and units of a glycolcomponent. The units of the diacid component can be derived from a firstacid and a second acid. A process can be used to form the article thatincludes depositing a plurality of layers of a polymeric material onto asubstrate. In some cases, the plurality of layers are deposited onto thesubstrate according to a predetermined design.

An article can also comprise a body including a polymeric material thatincludes units of a diacid component and units of a glycol component,where the units of the diacid component are derived from a first acidand a second acid. The body of the article can have a diameter fromabout 1 mm to about 5 mm and a length of at least about 3 cm. Thearticle can be formed by a process that includes combining a diacidcomponent and a glycol component to form a polymeric material andextruding the polymeric material to form a filament.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description is described with reference to the accompanyingfigures. In the figures, the left-most digit(s) of a reference numberidentifies the figure in which the reference number first appears. Thesame reference numbers in different figures indicates similar oridentical items.

FIG. 1 illustrates example components of a first example additivemanufacturing system.

FIG. 2 illustrates example components of a second example additivemanufacturing system.

FIG. 3 illustrates a side view of multiple layers of an object beingdeposited onto a substrate during an additive manufacturing process.

FIG. 4 is a flow diagram of an example process of forming an object on asubstrate by depositing a plurality of layers of a polymeric materialonto a substrate and removing the object from the substrate.

FIG. 5 shows an example object produced from a first polymeric materialat an extrusion rate of about 1 mm3/s where the filament is heated atdifferent temperatures before extruding the filament to form the object.

FIG. 6 shows another example object produced from a second polymericmaterial at an extrusion rate of about 2 mm3/s, where the filament isheated at different temperatures before extruding the filament to formthe object.

FIG. 7 shows an object produced from the first polymeric material at atemperature of about 235° C. using an extrusion based additivemanufacturing apparatus, where the extrusion rate at which the layers ofthe object were formed increased with increasing height of the object.

FIG. 8 shows an object produced from the second polymeric material at atemperature of about 235° C. using an extrusion based additivemanufacturing apparatus, where the extrusion rate at which the layers ofthe object were formed increased with increasing height of the object.

DETAILED DESCRIPTION

The present disclosure is directed to, among other things, techniques,systems, and materials for producing objects using an additivemanufacturing system. An object can be produced by depositing one ormore layers of a build material on a surface of the substrate accordingto a predetermined design, which may be based on three-dimensional (3D)model data. The build material can be formed in the shape of a filament.The filament can be formed by combining a glycol component and a diacidcomponent to produce a polymeric material and extruding the polymericmaterial. In some cases, the polymeric material can include aco-polyester having units derived from cyclohexanedimethanol and unitsderived from terephthalic acid, isophthalic acid,cyclohexanedicarboxylic acid, naphthalenedicarboxylic acid,stilbenedicarboxylic acid, 2,2,4,4-Tetramethyl-1,3-cyclobutanediol, or acombination thereof.

The object formed using the techniques, systems, and materials disclosedherein can be intended for any suitable application including, withoutlimitation, modeling, rapid prototyping, production, and the like.Additionally, the system used to create the object can be implemented inany suitable context including end-consumer systems, prosumer systems,or professional-grade additive manufacturing systems. For example,additive manufacturing systems, such as extrusion-based 3D printers, andmaterials for implementing the techniques disclosed herein can bemanufactured and sold to consumers for at-home building of objects(e.g., “do-it-yourself” 3D printing kits, desktop 3D printers, packagesincluding the substrate (e.g., a polymeric sheet) for use in 3Dprinters, and the like). A “package,” as used herein, is meant todescribe a collection of items or components that are packaged forcommercial sale to consumers and usable as, or with, an additivemanufacturing system. To illustrate, a package can include a filament ofa build material. In addition, components of an additive manufacturingsystem can be offered as a bundle package, such as a 3D printer, buildmaterial filament, and/or a substrate that is to be used in the 3Dprinter to form objects. Instructions may be included in, or on, thepackage as well (e.g., printed text on the package or on a slip of paperinside the package), instructing a consumer to use the packaged contentsin a specified manner.

Additionally, or alternatively, the materials and processes describedherein can be implemented to mass manufacture objects with highthroughput at additive manufacturing facilities. Industries that canbenefit from the techniques, systems, and materials described hereininclude, without limitation, cosmetics (e.g., cosmetic containermanufacturing), beverage container manufacturing, product enclosuremanufacturing, and so on.

The techniques and systems disclosed herein can result in polymericmaterials that can be used to form objects using additive manufacturingtechniques. The polymeric materials can include properties that areconducive to forming the polymeric materials into a filament. Forexample, polymeric materials described herein for forming objects usingadditive manufacturing processes can have physical properties thatenable the polymeric materials to be subject to extrusion and also to berolled into a filament.

The polymeric materials can also have physical attributes that areconducive to additive manufacturing processes. To illustrate, thepolymeric materials can have a viscosity and melt stability attemperatures utilized to form objects using additive manufacturingsystems. In particular, the polymeric materials described herein have aviscosity that enables the polymeric materials to flow through anextrusion head with minimal, if any, clogging. Additionally, the meltstability of the polymeric materials minimizes degradation of thepolymeric materials at temperatures that can be used to produce objectsusing additive manufacturing techniques.

Further, the polymeric materials can have physical properties thatminimize shrinkage after extrusion and also provide sufficient adhesionwith a substrate on which an object is being formed. Sufficient adhesionbetween the substrate and a build material used to form an object viaadditive manufacturing can minimize defects in the object. In manysituations, selecting a build material, substrate, and additivemanufacturing system to achieve sufficient adhesion characteristics atan interface between the substrate and the object can be based on anumber of factors. For example, if a partially completed object does nothave sufficient adhesion with the substrate, the partially completedobject can move and change its position on the substrate. Accordingly,subsequent layers of the build material can be deposited in a mannerthat causes a shape of the object to deviate from an intended shape. Inanother example, without sufficient adhesion between a build materialand the substrate on which an object is being formed, the partiallycompleted object can become detached from the substrate preventing thecompletion of the object.

Further, there can be some defects in objects that are caused by theadhesion between a build material used to form an object and thesubstrate on which the object is formed. In particular, the substrate,the object, or both can be damaged in some way when the object isremoved from the substrate. For example, a physical object or tool, suchas a chisel or knife, or a chemical process may be used to remove anobject from the substrate and cause damage to the object and/orsubstrate, such as causing chips or flakes of material to be separatedfrom the body of the object or the substrate.

The techniques and systems described herein can be implemented in anumber of ways. Example implementations are provided below withreference to the following figures.

FIG. 1 illustrates example components of a first example additivemanufacturing system 100. The system 100 can be configured tomanufacture objects by utilizing additive manufacturing principles. Forexample, the system 100 can be considered a fused deposition Modeling®(FDM®) system, a fused filament fabrication (FFF) system, or moregenerally, a 3D printing system (or 3D printer). In particular, thesystem 100 can be used to produce an object 102 by depositing layers ofa build material on a substrate 104 that is disposed on a platform 106.After the object 102 is completed, the object 102 can be separated fromthe substrate 104. In some cases, the object 102 can be removed from thesubstrate 104 by hand, with a tool, by bending the substrate, orcombinations thereof. In other cases, a layer can be formed on thesubstrate 104 that can aid in the removal of the object 102 from thesubstrate 104. To illustrate, a water-dispersible layer can be formedbetween layers of the object 102 and the substrate 104. Thewater-dispersible layer can include material that provides sufficientadhesion between the substrate 104 and the layers of the object 102 suchthat defects can be minimized in the formation of the object 102. Theobject 102 can be removed from the substrate 104 by breaking down thewater-dispersible layer through contact with an amount of water.

The substrate 104 can be positioned on the platform 106, where theplatform 106 is configured to support the substrate 104. In this manner,the substrate 104 can be provided on the platform 106 as a “workingsurface” for building the object 102 on the substrate 104. The substrate104 can include a glass material, in some cases. In other cases, thesubstrate 104 can include one or more polymeric materials.

The substrate 104 can be removably mounted, attached, or fastened to theplatform 106 using an attachment mechanism including, withoutlimitation, one or more bolts, clamps, hooks, latches, locks, nails,nuts, pins, screws, slots, retainers, adhesive, Velcro®, tape, or anyother suitable attachment mechanism that allows for the substrate 104 tobe secured to the platform 106 during the formation of the object 102,yet to also be removable after the object 102 is formed. In some cases,suction can be applied to the substrate 104 to hold the substrate 104 inplace during formation of the object 102. For example, one or more holescan be provided in the platform 106 and suction, or a vacuum, can beapplied via the one or more holes to force the substrate 104 toward theplatform 106. In some examples, mounting the substrate 104 on theplatform 106 can include setting (laying or placing) the substrate 104on the platform 106 without any additional securing mechanism.

The system 100 can include a housing 108 for a number of the componentsof the system 100. The housing 108 can be formed from a number ofmaterials, such as one or more metals, one or more polymers, or acombination thereof. The system 100 can also include an extrusion head110. The extrusion head 110 can be configured to extrude build materialonto the substrate 104 during the process of forming the object 102. Theextrusion head 110 can be any suitable type of extrusion head 110configured to receive material and to extrude the material through anozzle (or tip) that includes an orifice from which fluent strands or“roads” of the build material can be deposited onto the substrate 104 ina layer-by-layer manner to form the object 102. Nozzles of varying-sizedorifices can be utilized for depositing roads of build material havingdifferent thicknesses from the extrusion head 110.

The extrusion head 110 can include a heating element that heats thebuild material to a temperature that causes the build material to becomeflowable before extruding the build material onto the substrate 104. Thetemperature applied to heat the build material in the extrusion head 110can be at least about 180° C., at least about 190° C., at least about200° C., or at least about 210° C. Additionally, the temperature appliedto heat the build material in the extrusion head 112 can be no greaterthan about 260° C., no greater than about 250° C., no greater than about240° C., no greater than about 230° C., or no greater than about 220° C.In an illustrative example, the temperature applied to heat the buildmaterial in the extrusion head 110 can be included in a range of about175° C. to about 275° C. In another illustrative example, thetemperature applied to heat the build material in the extrusion head 112can be included in a range of about 195° C. to about 245° C. In anadditional illustrative example, the temperature applied to heat thebuild material in the extrusion head 112 can be included in a range ofabout 220° C. to about 240° C.

During operation of the system 100, the substrate 104 can be initiallypositioned below the extrusion head 110 in a direction along the Z-axisshown in FIG. 1 at a time prior to the first layer of build materialbeing deposited. The distance at which the substrate 104 is spaced belowthe extrusion head 110 can be any suitable distance allowing for thedeposition of fluent strands or “roads” of build material at a desiredthickness. In some instances, a distance between the substrate 104 andthe extrusion head 110 prior to deposition of the first layer of buildmaterial can be from about 0.02 mm to about 4 mm. As layers of the buildmaterial are deposited to form the object 102, the extrusion head 110can be moved a distance in increments in the Z-direction that allows fordepositing a next layer of build material at a specified thickness. Insome examples, the incremented distance can be about 0.1 mm.

The extrusion head 110 can be coupled to a horizontal rail 112. Theextrusion head 110 can move along the horizontal rail 112 in theX-direction. The extrusion head 110 can move along the horizontal rail112 by the use of one or more stepper motors, one or more servo motors,one or more microcontrollers, one or more belts, combinations thereof,and the like. The system 100 can also include a first vertical rail 114and a second vertical rail 116. Optionally, the horizontal rail 112 canbe coupled to the first vertical rail 114 and the second vertical rail116, such that the horizontal rail 112 can move vertically in theZ-direction along the first vertical rail 114 and the second verticalrail 116.

The extrusion head 110 can move along the horizontal rail 112 and/or thefirst vertical rail 114 and the second vertical rail 116 at a speed ofat least about 5 mm/second, at least about 10 mm/second, at least about25 mm/second, at least about 50 mm/second, at least about 75 mm/secondor at least about 125 mm/second. In addition, the extrusion head 110 canmove along the horizontal rail 112 and/or the first vertical rail 114and the second vertical rail 116 at a speed no greater than about 400mm/second, no greater than about 350 mm/second, no greater than about300 mm/second, no greater than about 250 mm/second, no greater thanabout 200 mm/second, or no greater than about 150 mm/second. In anillustrative example, the extrusion head 110 can move along thehorizontal rail 112 and/or the first vertical rail 114 and the secondvertical rail 116 at a speed included in a range of about 2 mm/second toabout 500 mm/second. In another illustrative example, the extrusion head110 can move along the horizontal rail 112 and/or the first verticalrail 114 and the second vertical rail 116 at a speed included in a rangeof about 20 mm/second to about 300 mm/second. In an additionalillustrative example, the extrusion head 110 can move along thehorizontal rail 112 and/or the first vertical rail 114 and the secondvertical rail 116 at a speed included in a range of about 30 mm/secondto about 100 mm/second.

The system 100 can also include a material source 118 that stores abuild material for forming objects using the system 100. The materialsource 118 can be coupled to the extrusion head 110 by a supply line120. The material source 118 can include a material bay or housingcontaining a spool of build material filament that can be unwound fromthe spool by a motor or drive unit. In some examples, supplying of thebuild material through the supply line 120 can be turned on or off, andthe build material can be advanced in both forward and backwarddirections along the supply line 120. Retraction of the build materialalong the supply line 120 toward the material source 118 can minimize“drool” at the extrusion head 110 and/or allow for recycling of unusedbuild material after finishing the object 102. Moreover, the rate atwhich the build material is supplied to the extrusion head 110 can becontrolled by a drive unit (e.g., worm drive) at varying speeds so thatspeeds can be increased or decreased.

An extrusion rate at which the build material flows through theextrusion head 110 can be at least about 3 mm³/s, at least about 3.5mm³/s, at least about 4 mm³/s, at least about 4.5 mm³/s, at least about5 mm³/s, at least about 5.5 mm³/s, at least about 6 mm³/s, at leastabout 10 mm³/s, at least about 20 mm³/s, at least about 50 mm³/s, atleast about 100 mm³/s, at least about 200 mm³/s, at least about 500mm³/s, at least about 1000 mm³/s, or at least about 2000 mm³/s. Also, anextrusion rate at which the build material flows through the extrusionhead 110 can be no greater than about 10 mm³/s, no greater than about9.5 mm³/s, no greater than about 9 mm³/s, no greater than about 8.5mm³/s, no greater than about 8 mm³/s, no greater than about 7.5 mm³/s,no greater than about 7 mm³/s, or no greater than about 6.5 mm³/s. In anillustrative example, an extrusion rate at which the build materialflows through the extrusion head 110 can be from about 2 mm³/s to about8400 mm³/s. In an illustrative example, an extrusion rate at which thebuild material flows through the extrusion head 110 can be from about 2mm³/s to about 12 mm³/s. In another illustrative example, an extrusionrate at which the build material flows through the extrusion head 110can be from about 4 mm³/s to about 10 mm³/s. In an additionalillustrative example, an extrusion rate at which the build materialflows through the extrusion head can be from about 7 mm³/s to about 9mm³/s. In an illustrative example, an extrusion rate at which the buildmaterial flows through the extrusion head can be from about 7 mm³/s toabout 8400 mm³/s. In an illustrative example, an extrusion rate at whichthe build material flows through the extrusion head can be from about100 mm³/s to about 8400 mm³/s.

The build material stored by the material source 118 can include apolymeric material. For example, the build material can include athermoplastic polymer. To illustrate, the build material can include athermoplastic resin. Additionally, the build material can include apolyester. Further, the build material can include a copolymer.Optionally, the build material can include a copolyester.

The build material can include units of an acid component and units of aglycol component. The units of the acid component can be derived fromone or more particular acids, while the units of the glycol componentcan be derived from one or more particular glycols. Additionally, thebuild material can include 100 mole % of the acid component and 100 mole% of the glycol component. In some cases, a portion of the glycolcomponent or a portion of the acid component can include a branchingagent. For example, the acid component or the glycol component caninclude at least about 0.1 mole % of a branching agent or no greaterthan about 1.5 mole % of a branching agent. The branching agent caninclude one or more of trimellitic anhydride, trimellitic acid,pyromellitic dianhydride, trimesic acid, hemimellitic acid, glycerol,trimethylolpropane, pentaerythritol, 1,2,4-butanetriol,1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakis(hydroxymethy)cyclohexane,di pentaerythritol, or combinations thereof.

The acid component can include units derived from one or more acids. Insome cases, the acid component can include a diacid component. Forexample, the acid component can include units of a first acid and unitsof one or more second acids. To illustrate, the first acid can includeterephthalic acid. In addition, the one or more second acids can beselected from a group of diacids including isophthalic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, anaphthalenedicarboxylic acid, a stilbenedicarboxylic acid, sebacic acid,dimethylmalonic acid, succinic acid, or combinations thereof. In someparticular examples, the naphthalenedicarboxylic acid can include1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,2,6-naphthalenedicarboxylic acid, or 2,7-naphthalenedicarboxylic acid.

The acid component can include at least about 30 mole % of units derivedfrom the first acid, at least about 35 mole % of units derived from thefirst acid, at least about 38 mole % of units derived from the firstacid, at least about 42 mole % of units derived from the first acid, atleast about 45 mole % of units derived from the first acid, at leastabout 48 mole % of units derived from the first acid, at least about 50mole % of units derived from the first acid, or at least about 52 mole %of units derived from the first acid. In addition, the acid componentcan include no greater than about 75 mole % of units derived from thefirst acid, no greater than about 70 mole % of units derived from thefirst acid, no greater than about 68 mole % of units derived from thefirst acid, no greater than about 65 mole % of units derived from thefirst acid, no greater than about 62 mole % of units derived from thefirst acid, no greater than about 60 mole % of units derived from thefirst acid, no greater than about 58 mole % of units derived from thefirst acid, or no greater than about 55 mole % of units derived from thefirst acid. In an illustrative example, the acid component can includefrom about 30 mole % to about 75 mole % of units derived from the firstacid. In another illustrative example, the acid component can includefrom about 35 mole % to about 65 mole % of units derived from the firstacid. In an additional illustrative example, the acid component caninclude from about 40 mole % to about 60 mole % of units derived fromthe first acid. In a further illustrative example, the acid componentcan include from about 45 mole % to about 55 mole % of units derivedfrom the first acid.

Additionally, the acid component can include at least about 30 mole % ofunits derived from the one or more second acids, at least about 35 mole% of units derived from the one or more second acids, at least about 38mole % of units derived from the one or more second acids, at leastabout 42 mole % of units derived from the one or more second acids, atleast about 45 mole % of units derived from the one or more secondacids, at least about 48 mole % of units derived from the one or moresecond acids, at least about 50 mole % of units derived from the one ormore second acids, or at least about 52 mole % of units derived from theone or more second acids. In addition, the acid component can include nogreater than about 75 mole % of units derived from the one or moresecond acids, no greater than about 70 mole % of units derived from theone or more second acids, no greater than about 68 mole % of unitsderived from the one or more second acids, no greater than about 65 mole% of units derived from the one or more second acids, no greater thanabout 62 mole % of units derived from the one or more second acids, nogreater than about 60 mole % of units derived from the one or moresecond acids, no greater than about 58 mole % of units derived from theone or more second acids, or no greater than about 55 mole % of unitsderived from the one or more second acids. In an illustrative example,the acid component can include from about 30 mole % to about 75 mole %of units derived from the one or more second acids. In anotherillustrative example, the acid component can include from about 35 mole% to about 65 mole % of units derived from the one or more second acids.In an additional illustrative example, the acid component can includefrom about 40 mole % to about 60 mole % of units derived from the one ormore second acids. In a further illustrative example, the acid componentcan include from about 45 mole % to about 55 mole % of units derivedfrom the one or more second acids.

Further, the acid component can include, in some cases, amounts of unitsderived from additional acids, such as additional aliphatic dibasicacids having 4 to about 40 carbon atoms, additional cycloaliphaticdibasic acids having about 4 to about 40 carbon atoms, additionalaromatic dibasic acids having about 4 to about 40 carbon atoms, orcombinations thereof. In a particular example, the acid component caninclude no greater than about 10 mole % of units derived from one ormore of the additional acids, no greater than about 8 mole % of unitsderived from one or more of the additional acids, no greater than about6 mole % of units derived from one or more of the additional acids, orno greater than about 4 mole % of units derived from one or more of theadditional acids. Additionally, the acid component can include at leastabout 0.5 mole % of units derived from one or more of the additionalacids, at least about 1 mole % of units derived from one or more of theadditional acids, or at least about 2 mole % of units derived from oneor more of the additional acids. In an illustrative example, the acidcomponent can include from about 0.5 mole % to about 10 mole % of unitsderived from one or more of the additional acids.

Optionally, esters of the acids can be used to form the polymericmaterial of the build material. In an example, lower alkyl esters of theacids can be used to form the polymeric material. In a particularexample, methyl esters of the acids can be used to form the polymericmaterial. In an illustrative example, esters of terephthalic acid,esters of isophthalic acid, esters of 1,3-cyclohexanedicarboxylic acid,esters of 1,4 cyclohexanedicarboxylic acid, esters of anaphthalenedicarboxylic acid, esters of a stilbenedicarboxylic acid, orcombinations thereof, can be used to form the polymeric material.

The glycol component can include units derived fromcyclohexanedimethanol. Optionally, the polymeric material of the buildmaterial can include multiple glycols. For example, the glycol componentcan include units derived from a first glycol and units derived fromon-e or more second glycols. To illustrate, the first glycol can includecyclohexanedimethanol and the one or more second glycols can include oneor more glycols including about 2 to about 20 carbon atoms. In aparticular example, the one or more second glycols can include ethyleneglycol, 1,2-propanediol, 1,3-propanediol, neopentyl glycol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, p-xylene glycol, orcombinations thereof. In some cases, the build material can includepolyethylene glycols, polytetramethylene glycols,2,2,4,4-Tetramethyl-1,3-cyclobutanediol, or a combination thereof.

Optionally, when the glycol component includes units derived frommultiple glycols, the glycol component can include at least about 75mole % of units derived from the first glycol, at least about 78 mole %of units derived from the first glycol, at least about 80 mole % ofunits derived from the first glycol, at least about 82 mole % of unitsderived from the first glycol, or at least about 85% of units derivedfrom the first glycol. In addition, when the glycol component includesunits derived from multiple glycols, the glycol component can include nogreater than about 98 mole % of units derived from the first glycol, nogreater than about 95 mole % of units derived from the first glycol, nogreater than about 92 mole % of units derived from the first glycol, nogreater than about 90 mole % of units derived from the first glycol, orno greater than about 88 mole % of units derived from the first glycol.In an illustrative example, when the glycol component includes unitsderived from multiple glycols, the glycol component can include fromabout 75 mole % to about 98 mole % of units derived from the firstglycol. In another illustrative example, when the glycol componentincludes units derived from multiple glycols, the glycol component caninclude from about 85 mole % to about 95 mole % of units derived fromthe first glycol.

Furthermore, when the glycol component includes units derived frommultiple glycols, the glycol component can include no greater than about25 mole % of units derived from the one or more second glycols, nogreater than about 22 mole % of units derived from the one or moresecond glycols, no greater than about 20 mole % of units derived fromthe one or more second glycols, no greater than about 18 mole % of unitsderived from the one or more second glycols, no greater than about 15mole % of units derived from the one or more second glycols, or nogreater than about 12 mole % of units derived from the one or moresecond glycols. In some cases, when the glycol component includes unitsderived from multiple glycols, the glycol component can include at leastabout 1 mole % of units derived from the one or more second glycols, atleast about 3 mole % of units derived from the one or more secondglycols, at least about 5 mole % of units derived from the one or moresecond glycols, at least about 8 mole % of units derived from the one ormore second glycols, or at least about 10 mole % of units derived fromthe one or more second glycols. In an illustrative example, when theglycol component includes units derived from multiple glycols, theglycol component can include from about 2 mole % to about 25 mole % ofunits derived from the one or more second glycols. In anotherillustrative example, when the glycol component includes units derivedfrom multiple glycols, the glycol component can include from about 5mole % to about 15 mole % of units derived from the one or more secondglycols.

In one particular example, the polymeric material of the build materialcan be comprised of an acid component including from about 48 mole % toabout 55 mole % units derived from terephthalic acid and from about 44mole % to about 52 mole % units derived from isophthalic acid and aglycol component including units derived from 1,4-cyclohexanedimethanol.In another particular example, the polymeric material can be comprisedof an acid component including from about 47 mole % to about 53 mole %units derived from terephthalic acid and from about 47 mole % to about53 mole % units derived from isophthalic acid and a glycol componentincluding units derived from 1,4-cyclohexanedimethanol.

Filament of the build material can have a diameter of at least about 0.5mm, at least about 1 mm, at least about 1.5 mm, or at least about 2 mm.In addition, filament of the build material can have a diameter nogreater than about 5 mm, no greater than about 4 mm, no greater thanabout 3 mm, or no greater than about 2.5 mm. In an illustrative example,the diameter of filament of the build material can be about 0.3 mm toabout 6 mm. In an additional illustrative example, the diameter of thefilament of the build material can be from about 1 mm to about 5 mm. Inanother illustrative example, the diameter of the filament of the buildmaterial can be from about 1.5 mm to about 3 mm. Further, filament ofthe build material can have a length from about 3 cm to about 10 cm,from about 15 cm to about 25 m, from about 30 cm to about 5 m, or fromabout 50 cm to about 1 m. In some cases, filament of the build materialcan have a length of at least about 3 cm, at least about 5 cm, at leastabout 10 cm, at least about 20 cm, at least about 30 cm, at least about50 cm, at least about 1 m, at least about 2 m, or at least about 5 m. Inother cases, filament of the build material can have a length no greaterthan about 25 m, no greater than about 20 m, no greater than about 15 m,no greater than about 12 m, no greater than about 10 m, no greater thanabout 8 m, or no greater than about 6 m. Additionally, filament of thebuild material can have a length of no greater than about 500 m, nogreater than about 400 m, no greater than about 300 m, no greater thanabout 200 m, no greater than about 100 m, or no greater than about 50 m.In an illustrative example, filament of the build material can have alength from about 10 m to 500 m. In another illustrative example,filament of the build material can have a length from about 25 m toabout 300 m. In an additional illustrative example, filament of thebuild material can have a length from about 50 m to about 200 m.

Optionally, the platform 106 can be heated to aid in the adhesion of theobject 102 to the substrate 104 during the formation of the object 102.In an illustrative example, the platform 106 can be heated at atemperature included in a range of about 30° C. to about 125° C. Heatingof the platform 106 can be performed by any suitable heating elements,such as electrical elements that can be turned on or off, gas heatingelements below the platform 106, or any other suitable heating element.In some situations, though, the platform 106 may not be heated. Inanother illustrative example, the platform 106 can be heated at atemperature included in a range of about 40° C. to about 90° C. In someinstances, the temperature at which the platform 106 is heated candepend on a glass transition temperature of the build material beingdeposited onto the substrate 104 to form the object 102. Further,heating the platform 106 can provide an anti-warping effect on the buildmaterial used to form the object 102.

The system 100 can include a control system 122. The control system 122can include one or more hardware processor devices and one or morephysical memory devices. The one or more physical memory devices can beexamples of computer storage media for storing instructions which areexecuted by the one or more processors to perform various functions. Theone or more physical memory devices can include both volatile memory andnon-volatile memory (e.g., RAM, ROM, or the like). The one or morephysical memory devices can also include one or more cache memorydevices, one or more buffers, one or more flash memory devices, or acombination thereof. The system 100 can also include one or moreadditional components, such as one or more input/output devices. Forexample, the system 100 can include a keyboard, a mouse, a touch screen,a display, speakers, a microphone, a camera, combinations thereof, andthe like. The system 100 can also include one or more communicationinterfaces for exchanging data with other devices, such as via anetwork, direct connection, or the like. For example, the communicationinterfaces can facilitate communications within a wide variety ofnetworks or connections, such as one or more wired networks or wiredconnections and/or one or more wireless networks or wirelessconnections.

The control system 122 can include, be coupled to, or obtain data from acomputer-aided design (CAD) system to provide a digital representationof the object 102 to be formed by the system 100. Any suitable CADsoftware program can be utilized to create the digital representation ofthe object 102. For example, a user can design, using a 3D modelingsoftware program executing on a host computer, an object having aparticular shape with specified dimensions, such as the object 102, thatis to be manufactured using the system 100. In order to translate thegeometry of the object 102 into computer-readable instructions orcommands usable by a processor or a suitable controller in forming theobject 102, the control system 122 can mathematically slice the digitalrepresentation of the object 102 into multiple horizontal layers. Thecontrol system 122 can then design build paths along which buildmaterial is to be deposited in a layer-by-layer fashion to form theobject 102.

The control system 122 can manage and/or direct one or more componentsof the system 100, such as the extrusion head 110, by controllingmovement of those components according to a numerically controlledcomputer-aided manufacturing (CAM) program along computer-controlledpaths. Optionally, the control system 122 can control one or morecomponents of the system 100 to move according to script written in aprogramming language, such as Python. The script can be used to producecode in a numerical programming language, such as G-code, that thecontrol system 122 can execute. The movement of the various componentsof the system 100, such as the extrusion head 110, can be performed bythe use of stepper motors, servo motors, microcontrollers, combinationsthereof, and the like.

As build material is supplied to the extrusion head 110, the controlsystem 122 directs the movement of the extrusion head 110 along thehorizontal rail 112 and/or the vertical rails 114, 116 so that theextrusion head 110 can follow a predetermined build path whiledepositing build material for each layer of the object 102. In thissense, the rails 112, 114, 116 allow the extrusion head 110 to movetwo-dimensionally and/or three-dimensionally in vertical and/orhorizontal directions as shown by the arrows in FIG. 1. Additionally, oralternatively, the platform 106 can be movable in two-dimensions and/orthree-dimensions, and such movement can be controlled by the controlsystem 122 to provide similar relative movement between the substrate104 and platform 106 and the extrusion head 110 so that multiple roadsof build material can be deposited by moving the extrusion head 110and/or the platform 106 in a two-dimensional (2D) horizontal plane(i.e., X-Y plane) to form each layer of the object 102, and thenmultiple successive layers can be deposited on top of one another bymoving the extrusion head 110 and/or the platform 106 in a verticalZ-direction.

Optionally, the substrate 104, the build material of the material source118, or a combination thereof, can be included in a package that can bepurchased and used in conjunction with the system 100. The package canalso include instructions on how to form objects using the filament ofbuild material with the system 100. For example, the instructions canindicate settings for the system 100, such as a temperature to heat thebuild material in the extrusion head 110, that correspond with thecomposition of the filament of build material.

The object 102 can be formed in a controlled environment, such as byconfining individual ones of the components of the system 100 to achamber or other enclosure formed by the housing 108 where temperature,and optionally other parameters (e.g., pressure) can be controlled andmaintained at a desired level by elements configured to controltemperature, pressure, etc. (e.g., heating elements, pumps, etc.). Insome instances, the temperature applied to the build material cancorrespond to a temperature at or above the creep-relaxation temperatureof the build material. This can allow more gradual cooling of the buildmaterial as it is deposited onto the substrate 104 so as to preventwarping of the layers of the object 102 upon deposition.

Although FIG. 1 illustrates one illustrative example of certaincomponents of an additive manufacturing system usable for carrying outthe techniques disclosed herein, it is to be appreciated that theconfiguration and inclusion of certain components shown in FIG. 1 isone, non-limiting, example of a suitable additive manufacturing system.Namely, other types and configurations of additive manufacturing systemscan be utilized with the techniques and materials disclosed hereinwithout changing the basic characteristics of the additive manufacturingsystem 100, and the additive manufacturing system 100 can be implementedas any suitable size for a particular industry or application, such asindustrial-sized for commercial object production and/or testing,desktop-sized, handheld for consumer-use, and so on. For example, ahandheld additive manufacturing system can be utilized to form theobject 102 on the substrate 104 or a conveyor arrangement can beutilized to form the object 102 on the substrate 104. One illustrativeexample of a suitable handheld system is the 3Doodler®, a 3D printingpen from WobbleWorks LLC.

FIG. 2 illustrates example components of a second example additivemanufacturing system 200. The system 200 is similar to that of theadditive manufacturing system 100 of FIG. 1, except that the system 200is arranged in a delta machine configuration. Thus, some components ofthe system 200 are not shown in FIG. 2 and the details with respect tosome of the components of the system 200 shown in FIG. 2 are omittedbecause the features of these components have been described previouslyin the description of FIG. 1.

The system 200 can include an extrusion head 202 that is coupled to afirst arm 204, a second arm 206, and a third arm 208. The first arm 204can be movably coupled to a first rail 210, the second arm 206 can bemovably coupled to a second rail 212, and the third arm 208 can bemovably coupled to a third rail 214. In addition, the extrusion head 214can be coupled to the first arm 204, the second arm 206, and the thirdarm 208. Further, the system 200 can include a platform 216. Optionally,a substrate 218 can be disposed on the platform 216. In some cases, thesubstrate 218 can be removably attached to the platform 216.

The first arm 204, the second arm 206, and the third arm 208 can becontrolled by a control system (not shown) to move in a manner thatpositions the extrusion head 202 to form an object 220. In particular,the first arm 204, the second arm 206, and the third arm 208 can movethe extrusion head 202 according to a predetermined design to formlayers of the object 220. The polymeric material used to produce theobject 220 can be provided to the extrusion head 202 via a supply line222. In some cases, the supply line 222 can feed a filament into theextrusion head 202 to produce the object 220.

FIG. 3 illustrates a side view of multiple layers of an object 300 beingdeposited onto a substrate 302 during an additive manufacturing process.As discussed previously with reference to FIG. 1 and FIG. 2, during theadditive manufacturing process of forming an object on a substrate,build material is supplied to an extrusion head 304 and, optionally, thebuild material is heated. The build material is then deposited in roadsonto a surface. In the illustrative example of FIG. 3, the buildmaterial is deposited directly onto the substrate 302. In other cases,the build material can be deposited onto a layer (not shown) disposed onthe substrate 302, such as a layer that can be removed in order toseparate the object 300 from the substrate 302. A first layer 306(1) ofbuild material is shown as being deposited onto the substrate 302according to a predetermined build path, which can represent a beginningof the additive manufacturing process. As the extrusion head 304 movesat a predetermined speed according to a predetermined design for theobject 300, multiple additional layers 306(2), 306(3), 306(N−1), 306(N)of the build material can be deposited in a layer-by-layer fashion ontopreviously deposited layers to form the object 300 on the substrate 302.Depositing build material to form the layers 306(1)-306(N) can cause atleast a partial interface to be formed between each of the layers306(1)-306(N). The at least partial interface can be visible to a humaneye without or with aid, such as a type of microscope. For example, aninterface can be formed between the layer 306(1) and the layer 306(2).In another example, an interface can be formed between the layer 306(2)and the layer 306(3). The object 300 can be formed with 100% infill(i.e., a solid object), or with less than 100% infill (at least apartially hollow interior portion of the object 300).

The substrate 302 can include a glass material. In addition, thesubstrate 302 can include a polymeric material. In some cases, thesubstrate 302 can include a coating of the polymeric material. In otherinstances, the substrate 302 can be made substantially of the polymericmaterial. In an example, the substrate 302 can include a thermoplasticpolymer. The substrate 302 can also include a polyester. Additionally,the substrate 302 can include a glycol-modified polyethyleneterephthalate. Further, the substrate 302 can include a copolymer. Toillustrate, the substrate 302 can include a copolyester. Optionally, thesubstrate 302 can include a polylactic acid, an acrylonitrile butadienestyrene copolymer, a polycarbonate, a polyamide, a polyetherimide, apolystyrene, a polyphenylsulfone, a polysulfone, a polyethersulfone, apolyphenylene, a poly(methyl methacrylate), or a combination thereof.

The build material for the object 300 can include one or more polymericmaterials. The one or more polymeric materials can include any of thebuild materials described previously with respect to forming the object102 of FIG. 1. In a particular example, the build material for thelayers 306(1)-306(N) of the object 300 can comprise a copolyester havingunits of an acid component and units of a glycol component.

The build material used to form the layers 306(1)-306(N) can haveparticular physical properties that are conducive to forming objects inan additive manufacturing process. For example, the build material usedto form the layers 306(1)-306(N) can have an inherent viscosity of atleast about 0.4 dL/g, at least about 0.5 dL/g, at least about 0.55 dL/g,at least about 0.6 dL/g, or at least about 0.65 dL/g. Additionally, thebuild material used to form the layers 306(1)-306(N) can have aninherent viscosity of no greater than about 0.9 dL/g, no greater thanabout 0.8 dL/g, no greater than about 0.75 dL/g, or no greater thanabout 0.7 dL/g. In an illustrative example, the build material of thelayers 306(1)-306(N) can have an inherent viscosity from about 0.4 dL/gto about 0.9 dL/g. In another illustrative example, the build materialof the layers 306(1)-306(N) can have an inherent viscosity from about0.5 dL/g to about 0.8 dL/g. In an additional illustrative example, thebuild material of the layers 306(1)-306(N) can have an inherentviscosity from 0.55 dL/g to about 0.7 dL/g. The inherent viscosity canbe measured at about 25° C. in 100 ml of a 60/40 solution ofphenol/tetrachlorethane including about 0.5 g of the polymer.

Additionally, the build material used to form the layers 306(1)-306(N)can have a glass transition temperature of at least about 70° C., atleast about 72° C., at least about 75° C., at least about 78° C., or atleast about 80° C. Additionally, the build material used to form thelayers 306(1)-306(N) can have a glass transition temperature no greaterthan about 110° C., no greater than about 100° C., no greater than about95° C., no greater than about 92° C., no greater than about 90° C., nogreater than about 88° C., or no greater than about 85° C. In anillustrative example, the build material used to form the layers306(1)-306(N) can have a glass transition temperature from about 70° C.to about 110° C. In another illustrative example, the build materialused to form the layers 306(1)-306(N) can have a glass transitiontemperature from about 75° C. to about 100° C. In an additionalillustrative example, the build material used to form the layers306(1)-306(N) can have a glass transition temperature from about 80° C.to about 90° C. The glass transition temperature can be measured using adifferential scanning calorimeter (DSC) at a scan rate of about 20° C.

Further, the build material used to form the layers 306(1)-306(N) canhave a density of at least about 0.8 g/cm³, at least about 0.85 g/cm³,at least about 0.9 g/cm³, at least about 0.95 g/cm³, at least about 1g/cm³, or at least about 1.05 g/cm³. Optionally, the build material usedto form the layers 306(1)-306(N) can have a density no greater thanabout 1.35 g/cm³, no greater than about 1.30 g/cm³, no greater thanabout 1.25 g/cm³, no greater than about 1.2 g/cm³, no greater than about1.15 g/cm³, or no greater than about 1.1 g/cm³. In an illustrativeexample, the build material used to form the layers 306(1)-306(N) canhave a density from about 0.75 g/cm³ to about 1.4 g/cm³. In anotherillustrative example, the build material used to form the layers306(1)-306(N) can have a density from about 0.9 g/cm³ to about 1.3g/cm³. In a further illustrative example, the build material used toform the layers 306(1)-306(N) can have a density from about 1.15 g/cm³to about 1.25 g/cm³. The density can be measured using the AmericanSociety for Testing and Materials (ASTM) D 792 standard as of the dateof filing of this patent application.

Also, the build material used to form the layers 306(1)-306(N) can havea tensile strength at yield of at least about 30 MPa, at least about 35MPa, at least about 40 MPa, at least about 45 MPa, or at least about 50MPa. Further, the build material used to form the layers 306(1)-306(N)can have a tensile strength at yield no greater than about 80 MPa, nogreater than about 75 MPa, no greater than about 70 MPa, no greater thanabout 65 MPa, no greater than about 60 MPa, or no greater than about 55MPa. In an illustrative example, the build material used to form thelayers 306(1)-306(N) can have a tensile strength at yield from about 25MPa to about 100 MPa. In another illustrative example, the buildmaterial used to form the layers 306(1)-306(N) can have a tensilestrength at yield from about 35 MPa to about 60 MPa. In an additionalillustrative example, the build material used to form the layers306(1)-306(N) can have a tensile strength at yield from about 45 MPa toabout 55 MPa. The tensile strength at yield can be measured according tothe ASTM D638 standard at the time of filing of this patent application.

The build material used to form the layers 306(1)-306(N) can also havean elongation at break of at least about 80%, at least about 95%, atleast about 110%, at least about 125%, at least about 140%, or at leastabout 155%. In addition, the build material used to form the layers306(1)-306(N) can have an elongation at break of no greater than about230%, no greater than about 215%, no greater than about 200%, no greaterthan about 185%, or no greater than about 170%. In an illustrativeexample, the build material used to form the layers 306(1)-306(N) canhave an elongation at break from about 75% to about 250%. In anotherillustrative example, the build material used to form the layers306(1)-306(N) can have an elongation at break from about 95% to about205%. In an additional illustrative example, the build material used toform the layers 306(1)-306(N) can have an elongation at break from about80% to about 120%. In a further illustrative example, the build materialused to form the layers 306(1)-306(N) can have an elongation at breakfrom about 180% to about 220%. The elongation at break can be measuredaccording to the ASTM D638 standard at the time of filing of this patentapplication.

Additionally, the build material used to form the layers 306(1)-306(N)can have a crystallization half time of at least about 80 minutes, atleast about 90 minutes, at least about 100 minutes, at least about 110minutes, at least about 120 minutes, or at least about 130 minutes. Thebuild material used to form the layers 306(1)-306(N) can also have acrystallization half time of no greater than about 1000 minutes, nogreater than about 1000 minutes, no greater than about 750 minutes, nogreater than about 500 minutes, no greater than about 400 minutes, nogreater than about 300 minutes, or no greater than about 200 minutes. Inan illustrative example, the build material used to form the layers306(1)-306(N) can have a crystallization half time from about 75 minutesto about 1000 minutes. In another illustrative example, the buildmaterial used to form the layers 306(1)-306(N) can have acrystallization half time from about 100 minutes to about 400 minutes.In a further illustrative example, the build material used to form thelayers 306(1)-306(N) can have a crystallization half time from about 110minutes to about 180 minutes. The crystallization half time can bemeasured using a small angle light scattering technique using a heliumneon laser to measure the time at which the intensity of transmittedlight drops to half of the maximum intensity achieved while cooling asample to a predetermined temperature.

Optionally, the build material used to form the layers 306(1)-306(N) canhave a zero shear viscosity of at least about 1800 poise, at least about1900 poise, at least about 2000 poise, at least about 2100 poise, or atleast about 2200 poise. Also, the build material used to form the layers306(1)-306(N) can have a zero shear viscosity of no greater than about7000 poise, no greater than about 5000 poise, no greater than about 3000poise, no greater than about 2800 poise, no greater than about 2600poise, or no greater than about 2400 poise. In an illustrative example,the build material used to form the layers 306(1)-306(N) can have a zeroshear viscosity from about 1750 poise to about 8000 poise. In anadditional illustrative example, the build material used to form thelayers 306(1)-306(N) can have a zero shear viscosity from about 1800poise to about 4000 poise. In a further illustrative example, the buildmaterial used to form the layers 306(1)-306(N) can have a zero shearviscosity from about 1900 poise to about 3000 poise. The zero shearviscosity can be measured using small amplitude oscillatory sheartechniques with a frequency sweep from about 1 rad/s to about 400 rad/sat 260° C. using a 10% strain value where the viscosity measured at 1rad/s indicates the zero shear viscosity.

The build material used to form the layers 306(1)-306(N) can have aflexural modulus of at least about 1700 MPa, at least about 1750 MPa, atleast about 1800 MPa, at least about 1850 MPa, or at least about 1900MPa. Further, the build material used to form the layers 306(1)-306(N)can have a flexural modulus of no greater than about 2100 MPa, nogreater than about 2050 MPa, no greater than about 2000 MPa, or nogreater than about 1950 MPa. In an illustrative example, the buildmaterial used to form the layers 306(1)-306(N) can have a flexuralmodulus from about 1700 MPa to about 2100 MPa. In another illustrativeexample, the build material used to form the layers 306(1)-306(N) canhave a flexural modulus from about 1775 MPa to about 1975 MPa. Theflexural modulus can be determined according to the ASTM D790 standardat the time of filing of this patent application.

The build material used to form the layers 306(1)-306(N) can have anotched Izod impact strength of at least about 60 J/m, at least about 62J/m, at least about 64 J/m, at least about 66 J/m, or at least about 68J/m. In addition, the build material used to form the layers306(1)-306(N) can have a notched Izod impact strength of no greater thanabout 82 J/m, no greater than about 80 J/m, no greater than about 78J/m, no greater than about 76 J/m, no greater than about 74 J/m, or nogreater than about 72 J/m. In an illustrative example, the buildmaterial used to form the layers 306(1)-306(N) can have a notched Izodimpact strength from about 60 J/m to about 85 J/m. In anotherillustrative example, the build material used to form the layers306(1)-306(N) can have a notched Izod impact strength from about 65 J/mto about 75 J/m. The notched Izod impact strength can be determinedaccording to the ASTM D256 standard at 23° C. at the time of filing ofthis patent application.

Also, the build material used to form the layers 306(1)-306(N) can havea heat deflection temperature of at least about 52° C., at least about54° C., at least about 56° C., at least about 58° C., or at least about60° C. Further, the build material used to form the layers 306(1)-306(N)can have a heat deflection temperature of no greater than about 72° C.,no greater than about 70° C., no greater than about 68° C., no greaterthan about 66° C., no greater than about 64° C., or no greater thanabout 62° C. In an illustrative example, the build material used to formthe layers 306(1)-306(N) can have a heat deflection temperature fromabout 50° C. to about 72° C. In another illustrative example, the buildmaterial used to form the layers 306(1)-306(N) can have a heatdeflection temperature from about 55° C. to about 65° C. The heatdeflection temperature can be determined according to the ASTM D648standard at about 264 psi at the time of filing of this patentapplication.

The values of the physical properties of the build material used to formthe layers 306(1)-306(N) are conducive to forming objects, such as theobject 300, using an extrusion-based additive manufacturing process. Forexample, build material used to form the layers 306(1)-306(N) can have acrystallization half time of at least 100 minutes to minimize oreliminate the formation of haze in objects formed from the buildmaterials and to minimize shrinkage due to crystalline behavior inobjects formed from the build materials. Additionally, build materialsused to form the layers 306(1)-306(N) can have values for zero shearviscosity that enable the formation of objects using the build materialsat relatively low temperatures, such as less than 250° C. Buildmaterials having values of zero shear viscosity as described herein canalso reduce an amount of pressure in the extrusion head, which canfacilitate the formation of objects using extrusion-based additivemanufacturing on less robust equipment, that is, on equipment that isnot fitted to be able to withstand processing conditions underrelatively high pressure. Furthermore, the values of theglass-transition temperature and the values of the density of the buildmaterials used to form the layers 306(1)-306(N) impart heating andcooling characteristics of the build material within the extrusion head304 and outside of the extrusion head 304 such that the build materialcan flow through the extrusion head 304, while solidifying oncedeposited onto the substrate 302 or another layer such that defects ofthe object 300 are minimized. The build material used to form the layers306(1)-306(N) can also have an elongation at break that causes the buildmaterial to have minimal brittleness after extrusion. In addition, thebuild material used to form the layers 306(1)-306(N) can have aninherent viscosity that minimizes an amount of heat applied to the buildmaterial to cause the build material to flow and be extruded. Extrusionof the build material at minimized temperatures reduces degradation ofthe build material during extrusion and minimizes shrinkage of the buildmaterial after extrusion. The inherent viscosity of the build materialused to form the layers 306(1)-306(N) can also enable appropriate flowof the build material through the extrusion head 304 and cause theobject 300 to have a particular amount of strength after being formed.

The substrate 302 can have a thickness 308 and a length 310. Thesubstrate 302 can also have a width that is perpendicular to the length310. The substrate 302 can be of various shapes, including square,circular, rectangular, triangular, or any suitable polygonal shape.

The thickness 308 of the substrate 302 can be at least about 0.5 mm, atleast about 1 mm, or at least about 2 mm. Additionally, the thickness308 of the substrate 302 can be no greater than about 5 mm, no greaterthan about 4 mm, or no greater than about 3 mm. In an illustrativeexample, the thickness 308 of the substrate 302 can be included in arange of about 0.7 mm to about 4 mm. In another illustrative example,the thickness 308 of the substrate 302 can be included within a range ofabout 1 mm to about 2 mm.

The length 310 of the substrate 302 can be at least about 40 mm, atleast about 80 mm, at least about 120 mm, or at least about 150 mm.Additionally, the length 310 of the substrate 302 can be no greater thanabout 500 mm, no greater than about 400 mm, no greater than about 300mm, no greater than about 250 mm, or no greater than about 200 mm. In anillustrative example, the length 310 of the substrate 302 can beincluded in a range of about 30 mm to about 600 mm. In anotherillustrative example, the length 310 of the substrate 302 can beincluded in a range of about 40 mm to about 250 mm. In an additionalillustrative example, the length 310 of the substrate 302 can beincluded in a range of about 50 mm to about 200 mm.

Further, a width of the substrate 302 can be at least about 35 mm, atleast about 75 mm, at least about 125 mm, or at least about 160 mm. Thewidth of the substrate 302 can also be no greater than about 480 mm, nogreater than about 390 mm, no greater than about 310 mm, no greater thanabout 250 mm, or no greater than about 210 mm. In an illustrativeexample, the width of the substrate 302 can be included in a range ofabout 30 mm to about 600 mm. In another illustrative example, the widthof the substrate 302 can be included in a range of about 40 mm to about250 mm. In an additional illustrative example, the width of thesubstrate 302 can be included in a range of about 50 mm to about 200 mm.In some examples, a square-shaped substrate 302 can have a width of fromabout 100 mm to about 200 mm and have the length 312 of from about 100mm to about 200 mm.

The thickness (in the Z-direction of FIG. 3), of each of the layers306(1)-(N) of the object 300, such as a thickness 312, can be a valuethat provides a specified resolution to the object 300. That is, layershaving relatively greater values for thickness can result in anoticeably rigid or jagged outer surface of the object 300 (i.e., lowerresolution object), while layers having relatively lower values forthickness can make the separate layers inconspicuous and the object 300can have a smoother outer surface in both appearance and feel (i.e., ahigher resolution object). Furthermore, each of the layers 306(1)-(N)can be of substantially uniform thicknesses or of varying thicknesses.

A representative layer of the layers 306(1)-306(N), such as the layer306(N−1), can have a thickness 312 that is from about 5 micrometers toabout 2000 micrometers. In some cases, the thickness 312 can be fromabout 10 micrometers to about 1000 micrometers. Additionally, thethickness 312 can be from about 25 micrometers to about 500 micrometers.The thickness 312 can also be from about 35 micrometers to about 250micrometers.

The material of the substrate 302 and the build material of the layers306(1)-306(N) are selected to provide adhesion between the respectivelayers. For example, the material of the substrate 302 and the materialof the layer 306(1) can be selected to provide sufficient adhesionbetween the substrate 302 and the layer 306(1) such that the layer306(1) remains on the substrate 302 during the formation of the object300 while being removed from the substrate 302 with minimal, if any,damage to the object 300 or the substrate 302. Additionally, the buildmaterial of the layers 306(1)-306(N) can be selected such that anymovement of the layers 306(1)-306(N) is minimized to avoid or reduce anydeformation of the object 300.

FIG. 4 is a flow diagram of an example process 400 of forming an objecton a substrate by depositing a plurality of layers of a polymericmaterial onto a substrate and removing the object from the substrate.The process 400 is illustrated as a collection of blocks in a logicalflow graph, which represent a sequence of operations that can beimplemented, at least in part, by an extrusion-based additivemanufacturing system, such as the additive manufacturing system 100 ofFIG. 1, the additive manufacturing system 200 of FIG. 2, or both. Theorder in which the operations are described is not intended to beconstrued as a limitation, and any number of the described blocks can becombined in any order and/or in parallel to implement the process.

At 402, a substrate 404 can be provided for forming thereon an objectusing an additive manufacturing process. The substrate 404 can be thesame as or similar to the substrate 104 of FIG. 1, the substrate 204 ofFIG. 2, or the substrate 302 of FIG. 3. In some examples, the providingthe substrate 404 at 402 can comprise removably mounting or attaching apreformed substrate 404 to a platform, such as the platform 106 ofFIG. 1. In other examples, providing the substrate 404 at 402 canfurther comprise producing the substrate 404 by a suitable manufacturingtechnique, such as injection-molding, extrusion, blow-molding,compression molding, casting, or any other suitable method of making thesubstrate 402.

At 406, a filament 408 formed from a polymeric material including unitsof an acid component and units of a glycol component can be provided. Insome cases, providing the filament 408 at 406 can include combining adiacid component and a glycol component to form the polymeric material.For example, one or more diacids and one or more glycols can be mixedtogether. In some cases, the one or more diacids and the one or moreglycols can be in the form of pellets, powder, or some combinationthereof. In a particular example, pellets of at least one of the diacidcomponent or the glycol component can be subjected to a grindingoperation before being combined. The units of the acid component can bederived from one or more acids and the units of the glycol component canbe derived from one or more glycols. In a particular example, thepolymeric material can be produced via a condensation reaction betweenone or more acids and one or more glycols.

In some cases, the acid component of the polymeric material can includeunits derived from one or more dibasic acids. For example, the acidcomponent can include units derived from a terephthalic acid, unitsderived from an isophthalic acid, units derived from acyclohexanedicarboxylic acid, units derived from a naphthalenedicarboxylic acid, units derived from a stilbenedicarboxylic acid, orcombinations thereof. Optionally, the acid component can be comprised offrom about 40 mole % to about 60 mole % of units derived from a firstacid and from about 40 mole % to about 60 mole % of units derived from asecond acid. In a particular example, the acid component can becomprised of from about 45 mole % to about 55 mole % of units derivedfrom terephthalic acid and from about 45 mole % to about 55 mole % ofunits derived from isophthalic acid.

Additionally, the glycol component can include units derived fromcyclohexamedimethanol. Further, the glycol component can include unitsderived from one or more additional glycols, such as ethylene glycol,1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, p-xylene glycol,2,2,4,4-Tetramethyl-1,3-cyclobutanediol, or combinations thereof. Insome cases where the polymeric material includes units derived frommultiple glycols, the glycol component can include from about 75 mole %to about 98 mole % of units derived from a first glycol and from about 2mole % to about 25 mole % of units derived from one or more secondglycols.

The polymeric material of the filament 408 can also include additives,such as stabilizers, antioxidants, fillers, branching agents, pigments,dyes, combinations thereof, and the like.

Optionally, the polymeric material can have an intrinsic viscosity fromabout 0.55 dL/g to about 0.7 dL/g, a density no greater than about 1.25g/cm³, a glass transition temperature of at least about 80° C., and acrystallization half-time no greater than about 300 minutes. Also, thepolymeric material can have a zero shear viscosity no greater than about3000 Poise. Further, the polymeric material can have an elongation atbreak of at least about 75%.

After combining the diacid component and the glycol component to formthe polymeric material, the polymeric material can be extruded to formthe filament 408. In some cases, the polymeric material can be fed intothe extruder in the form of pellets, while in other cases, the polymericmaterial can be fed into the extruder as a powder. In particular, thefilament 408 of the build material can be produced using an extruder,such as a single screw extruder, in some instances, or a twin screwextruder, in other instances. In some cases, the extruder can include amelt pump, while in other cases, a melt pump can be absent from theextruder. When a single screw extruder or a twin screw extruder is usedto produce the filament 408, the screw(s) of the extruders can beoperated at a speed from about 50 rotations per minute to about 200rotations per minute. In an illustrative example, the speed of thesingle screw extruder or the twin screw extruder can be from about 75rotations per minute to about 175 rotations per minute. In anotherillustrative example, the speed of the single screw extruder or the twinscrew extruder can be from 60 rotations per minute to 85 rotations perminute. In addition, a feed rate into the extruder of one or morematerials used to form the filament 408 can be from 10 grams/minute to40 grams/minute, from 15 grams/minute to 35 grams/minute, from 20grams/minute to 30 grams per minute, or from 15 grams/minute to 25grams/minute.

The extruder can include one or more chambers and the mixture ofmaterials used to form the filament 408 can be heated in one or morechambers of the extruder. For example, heat can be applied to thepolymeric material in a first chamber of the extruder at a firsttemperature from 100° C. to 180° C., from 110° C. to 160° C., or from120° C. to 140° C. Also, heat can be applied to the polymeric materialused to form the filament 408 in a second chamber of the extruder at asecond, different temperature, such as from 160° C. to 260° C., from190° C. to 250° C., from 200° C. to 240° C., or from 210° C. to 230° C.When the extruder includes more than two chambers, heat can be appliedto the polymeric material used to form the filament 408 in one or moreadditional chambers of the extruder at the first temperature or thesecond temperature. In an illustrative example, heat can be applied tothe polymeric material used to form the filament 408 in one or morechambers of the extruder at a temperature from about 210° C. to about240° C.

The filament 408 can have a diameter from about 1 mm to about 5 mm and alength of at least about 3 cm. In some cases, the filament 408 can havea length of at least about 5 cm. In some cases, the filament 408 canhave a length of at least about 30 cm. In some cases, the filament 408can have a length from about 3 cm to about 5 m. In some cases, thefilament 408 can have a length from about 30 cm to about 5 m.Additionally, the filament 408 can have a length that is greater than 5m. In a particular example, the filament 408 can have a body with adiameter from about 1.5 mm to about 3 mm and a length of at least about2 m.

At 410, a plurality of layers of the polymeric material can be depositedonto the substrate 404 to produce an object 412. For example, the one ormore layers of the polymeric material can be extruded onto the substrate404 via an extrusion head according to a predetermined design to formthe object 412. To illustrate, the depositing of the one or more layersof the polymeric material onto the substrate 404 can occur based on apredetermined design to build the object 412 in a layer-by-layer fashionaccording to 3D model data processed by an additive manufacturingsystem. In some cases, an amount of the polymeric material can be heatedat a temperature from about 190° C. to about 270° C. before depositingthe amount of the polymeric material onto the substrate 404.

In addition, in depositing the plurality of layers of the filament 408onto the substrate 404, the polymeric material can be deposited at aspecified rate. In some cases, the filament 408 can be extruded onto thesubstrate 404 to produce the plurality of layers of the object. In thesecases, the rate at which the filament 408 is extruded can be referred toas the “rate of extrusion.” In an illustrative example, the rate atwhich the filament 408 is deposited onto the substrate 404 during theformation of the object 412 can be from about 5.5 mm³/s to about 9.5mm³/s. In another illustrative example, the rate at which the filament408 is deposited onto the substrate 404 during the formation of theobject 412 can be from about 6.5 mm³/s to about 9.0 mm³/s. In anadditional illustrative example, the rate at which the filament 408 isdeposited onto the substrate 404 during the formation of the object 412can be from about 7.6 mm³/s to about 8.7 mm³/s.

The object 412 can have an inherent viscosity of at least about 0.4dL/g, at least about 0.45 dL/g, at least about 0.50 dL/g, at least about0.55 dL/g, or at least about 0.60 dL/g. Additionally, the object 412 canhave an inherent viscosity of no greater than about 0.90 dL/g, nogreater than about 0.85 dL/g, no greater than about 0.80 dL/g, nogreater than about 0.75 dL/g, no greater than about 0.70 dL/g, or nogreater than about 0.65 dL/g. In an illustrative example, the object 412can have an inherent viscosity from about 0.35 dL/g to about 1.00 dL/g.In another illustrative example, the object 412 can have an inherentviscosity from about 0.50 dL/g to about 0.80 dL/g. In an additionalillustrative example, the object 412 can have an inherent viscosity fromabout 0.55 dL/g to about 0.70 dL/g. The inherent viscosity of the object412 can be measured in approximately a 60/40 solution ofphenol/tetrachloroethane at a concentration of about 0.5 g/100 ml atabout 25° C.

In some cases, the object 412 can have a minimal loss of inherentviscosity relative to an inherent viscosity of the polymeric materialused to produce the object 412. In particular, an inherent viscosityloss with inherent viscosity abbreviated as I.V. in the equation belowcan be expressed as:

${I.V.\mspace{14mu} {loss}} = {\frac{{polymeric}\mspace{14mu} {material}\mspace{14mu} {I.V.\mspace{11mu} {- \mspace{11mu} {object}}}\mspace{14mu} {I.V.}}{{polymeric}\mspace{14mu} {material}\mspace{14mu} {I.V.}} \times 100}$

In particular, the object 412 can have an inherent viscosity loss of nogreater than about 6%, no greater than about 5%, no greater than about4%, no greater than about 3%, no greater than about 2%, no greater thanabout 1.5%, no greater than about 1.3%, no greater than about 1.1%, nogreater than about 1%, no greater than about 0.9%, no greater than about0.7%, or no greater than about 0.5%. In some cases, the object can havesubstantially no inherent viscosity loss. In an illustrative example,the object 412 can have an inherent viscosity loss from about 0.01% toabout 10%. In another illustrative example, the object 412 can have aninherent viscosity loss from about 0.05% to about 8%. In an additionalillustrative example, the object 412 can have an inherent viscosity lossfrom about 0.10% to about 5%. In a further illustrative example, theobject 412 can have an inherent viscosity loss from about 0.5% to about2%.

Optionally, inherent viscosity loss can depend on a temperature at whichthe polymeric material of the filament 408 is heated as the layers ofthe polymeric material are deposited onto the substrate 404 during theformation of the object 412. To illustrate, when the object 412 isformed at a temperature of about 225° C., an inherent viscosity loss ofthe object 412 relative to the polymeric material of the filament 408can be no greater than about 2.5%, no greater than about 2.1%, nogreater than about 1.7%, no greater than about 1.5%, no greater thanabout 1.3%, no greater than about 1.1%, no greater than about 0.9%, nogreater than about 0.7%, no greater than about 0.5%, no greater thanabout 0.3%, or no greater than about 0.1%. In some cases, when theobject 412 is formed at a temperature of about 225° C., there can besubstantially no inherent viscosity loss of the object 412 relative tothe polymeric material of the filament 408. In an illustrative example,when the object 412 is formed at a temperature of about 225° C., aninherent viscosity loss of the object 412 relative to the polymericmaterial of the filament 408 can be from about 0.01% to about 3%. Inanother illustrative example, when the object 412 is formed at atemperature of about 225° C., an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be fromabout 0.04% to about 2.50%. In an additional illustrative example, whenthe object 412 is formed at a temperature of about 225° C., an inherentviscosity loss of the object 412 relative to the polymeric material ofthe filament 408 can be from about 0.1% to about 2%.

Additionally, when the object 412 is formed at a temperature of about230° C., an inherent viscosity loss of the object 412 relative to thepolymeric material of the filament 408 can be no greater than about5.5%, no greater than about 5.0%, no greater than about 4.5%, no greaterthan about 4%, no greater than about 3.5%, no greater than about 3%, nogreater than about 2.5%, no greater than about 2.0%, no greater thanabout 1.5%, no greater than about 1.0%, no greater than about 0.9%, nogreater than about 0.7%, no greater than about 0.5%, no greater thanabout 0.3%, or no greater than about 0.1%. In some cases, when theobject 412 is formed at a temperature of about 230° C., there can besubstantially no inherent viscosity loss of the object 412 relative tothe polymeric material of the filament 408. In an illustrative example,when the object 412 is formed at a temperature of about 230° C., aninherent viscosity loss of the object 412 relative to the polymericmaterial of the filament 408 can be from about 0.01% to about 6%. Inanother illustrative example, when the object 412 is formed at atemperature of about 230° C., an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be fromabout 0.04% to about 2.50%. In an additional illustrative example, whenthe object 412 is formed at a temperature of about 230° C., an inherentviscosity loss of the object 412 relative to the polymeric material ofthe filament 408 can be from about 0.1% to about 2%.

Further, when the object 412 is formed at a temperature of about 240°C., an inherent viscosity loss of the object 412 relative to thepolymeric material of the filament 408 can be no greater than about 6%,no greater than about 5.5%, no greater than about 5%, no greater thanabout 4.5%, no greater than about 4%, no greater than about 3.5%, nogreater than about 3%, no greater than about 2.5%, no greater than about2%, no greater than about 1.9%, no greater than about 1.7%, no greaterthan about 1.5%, no greater than about 1.3%, no greater than about 1.1%,or no greater than about 0.9%. In an illustrative example, when theobject 412 is formed at a temperature of about 240° C., an inherentviscosity loss of the object 412 relative to the polymeric material ofthe filament 408 can be from about 0.8% to about 6%. In anotherillustrative example, when the object 412 is formed at a temperature ofabout 240° C., an inherent viscosity loss of the object 412 relative tothe polymeric material of the filament 408 can be from about 1% to about4%. In an additional illustrative example, when the object 412 is formedat a temperature of about 240° C., an inherent viscosity loss of theobject 412 relative to the polymeric material of the filament 408 can befrom about 1.1% to about 2.1%.

Also, when the object 412 is formed at a temperature of about 250° C.,an inherent viscosity loss of the object 412 relative to the polymericmaterial of the filament 408 can be no greater than about 7.5%, nogreater than about 7%, no greater than about 6.5%, no greater than about6%, no greater than about 5.5%, no greater than about 5%, no greaterthan about 4.5%, no greater than about 4%, no greater than about 3.5%,no greater than about 3%, no greater than about 2.5%, no greater thanabout 2%, no greater than about 1.9%, no greater than about 1.7%, or nogreater than about 1.5%. In an illustrative example, when the object 412is formed at a temperature of about 250° C., an inherent viscosity lossof the object 412 relative to the polymeric material of the filament 408can be from about 2.3% to about 7.5%. In another illustrative example,when the object 412 is formed at a temperature of about 250° C., aninherent viscosity loss of the object 412 relative to the polymericmaterial of the filament 408 can be from about 2.7% to about 6.1%. In anadditional illustrative example, when the object 412 is formed at atemperature of about 250° C., an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be fromabout 2.8% to about 5.1%.

Furthermore, inherent viscosity loss can depend on a rate at which thepolymeric material of the filament 408 is deposited onto the substrate404 during the formation of the object 412. For example, when thefilament 408 is deposited onto the substrate 404 during the formation ofthe object 412 at a rate from about 7 mm³/s to about 8 mm³/s, aninherent viscosity loss of the object 412 relative to the polymericmaterial of the filament 408 can be no greater than about 5%, no greaterthan about 4.5%, no greater than about 4%, no greater than about 3.5%,no greater than about 3%, no greater than about 2.5%, no greater thanabout 2%, no greater than about 1.5%, no greater than about 1%, nogreater than about 0.9%, no greater than about 0.7%, no greater thanabout 0.5%, no greater than about 0.3%, or no greater than about 0.1%.In some cases, when the filament 408 is deposited onto the substrate 404during the formation of the object 412 at a rate from about 7 mm³/s toabout 8 mm³/s, there can be substantially no inherent viscosity loss ofthe object 412 relative to the polymeric material of the filament 408.In an illustrative example, when the filament 408 is deposited onto thesubstrate 404 during the formation of the object 412 at a rate fromabout 7 mm³/s to about 8 mm³/s, an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be fromabout 0.01% to about 6%. In another illustrative example, an inherentviscosity loss of the object 412 relative to the polymeric material ofthe filament 408 can be from about 0.7% to about 4.3%. In an additionalillustrative example, when the filament 408 is deposited onto thesubstrate 404 during the formation of the object 412 at a rate fromabout 7 mm³/s to about 8 mm³/s, an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be fromabout 0.9% to about 2.5%.

In addition, when the filament 408 is deposited onto the substrate 404during the formation of the object 412 at a rate from about 8 mm³/s toabout 9 mm³/s, an inherent viscosity loss of the object 412 relative tothe polymeric material of the filament 408 can be no greater than about5%, no greater than about 4.5%, no greater than about 4%, no greaterthan about 3.5%, no greater than about 3%, no greater than about 2.5%,no greater than about 2%, no greater than about 1.5%, no greater thanabout 1%, no greater than about 0.9%, no greater than about 0.7%, nogreater than about 0.5%, no greater than about 0.3%, or no greater thanabout 0.1%. In some cases, when the filament 408 is deposited onto thesubstrate 404 during the formation of the object 412 at a rate fromabout 8 mm³/s to about 9 mm³/s, there can be substantially no inherentviscosity loss of the object 412 relative to the polymeric material ofthe filament 408. In an illustrative example, when the filament 408 isdeposited onto the substrate 404 during the formation of the object 412at a rate from about 8 mm³/s to about 9 mm³/s, an inherent viscosityloss of the object 412 relative to the polymeric material of thefilament 408 can be from about 0.01% to about 4%. In anotherillustrative example, when the filament 408 is deposited onto thesubstrate 404 during the formation of the object 412 at a rate fromabout 8 mm³/s to about 9 mm³/s, an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be fromabout 0.1% to about 3.3%. In an additional illustrative example, whenthe filament 408 is deposited onto the substrate 404 during theformation of the object 412 at a rate from about 8 mm³/s to about 9mm³/s, an inherent viscosity loss of the object 412 relative to thepolymeric material of the filament 408 can be from about 0.2% to about0.9%.

In a particular example, when the object 412 is formed at a temperatureof about 230° C. and when the filament 408 is deposited onto thesubstrate 404 during the formation of the object 412 at a rate fromabout 7 mm³/s to about 8 mm³/s, an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be nogreater than about 5.5%, such as from about 0.7% to about 5.3%. Inanother particular example, when the object 412 is formed at atemperature of about 240° C. and when the filament 408 is deposited ontothe substrate 404 during the formation of the object 412 at a rate fromabout 7 mm³/s to about 8 mm³/s, an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be nogreater than about 5.5%, such as from about 1.5% to about 5.3%. In anadditional particular example, when the object 412 is formed at atemperature of about 250° C. and when the filament 408 is deposited ontothe substrate 404 during the formation of the object 412 at a rate fromabout 7 mm³/s to about 8 mm³/s, an inherent viscosity loss of the object412 relative to the polymeric material of the filament 408 can be nogreater than about 7.1%, such as from about 2.7% to about 6.8%.

Also, when the object 412 is formed at a temperature of about 230° C.and when the filament 408 is deposited onto the substrate 404 during theformation of the object 412 at a rate from about 8 mm³/s to about 9mm³/s, an inherent viscosity loss of the object 412 relative to thepolymeric material of the filament 408 can be no greater than about2.5%, such as from about 0.1% to about 2.3%. Additionally, when theobject 412 is formed at a temperature of about 240° C. and when thefilament 408 is deposited onto the substrate 404 during the formation ofthe object 412 at a rate from about 8 mm³/s to about 9 mm³/s, aninherent viscosity loss of the object 412 relative to the polymericmaterial of the filament 408 can be no greater than about 3.5%, such asfrom about 0.9% to about 3.3%. Further, when the object 412 is formed ata temperature of about 250° C. and when the filament 408 is depositedonto the substrate 404 during the formation of the object 412 at a ratefrom about 8 mm³/s to about 9 mm³/s, an inherent viscosity loss of theobject 412 relative to the polymeric material of the filament 408 can beno greater than about 6.1%, such as from about 2.5% to about 5.7%.

Inherent viscosity loss can indicate an amount of degradation of amaterial that occurs during an additive manufacturing process. The lossof inherent viscosity can cause a change in mechanical properties of amaterial. In some case, the change in mechanical properties can resultin an object produced using an additive manufacturing process beingbrittle.

Further, the object 412 can have a notched Izod test value from about 35kJ/m² to about 60 kJ/m². In another example, the object 412 can have anotched Izod test value from about 40 kJ/m² to about 55 kJ/m². In anadditional example, the object 412 can have a notched Izod test valuefrom about 45 kJ/m² to about 50 kJ/m². The notched Izod test value ofthe object 412 can be measured according to the ASTM D256 standard atthe time of filing of this patent application.

At 414, the object 412 can be removed from the substrate 404. In somecases, a machine, such as a robotic arm, can be used to remove theobject 412 from the substrate 404. In other cases, an individual canremove the object 412 from the substrate 404 by using a hand or tool.

Other architectures can be used to implement the describedfunctionality, and are intended to be within the scope of thisdisclosure. Furthermore, although specific distributions ofresponsibilities are defined above for purposes of discussion, thevarious functions and responsibilities might be distributed and dividedin different ways, depending on circumstances.

The concepts described herein will be further described in the followingexamples with reference to the following figures, which do not limit thescope of the disclosure described in the claims.

EXAMPLES Example 1

Samples of polymeric materials were prepared having the compositionsdescribed in Table 1. Samples 1 and 2 were formed according totechniques described herein and Samples 3 and 4 were prepared ascomparative examples. In addition to the components shown in Table 1,Sample 4 also included a trimellitic anhydride branching agent. Thecomposition of the samples was determined using proton nuclear magneticresonance spectroscopy (NMR).

TABLE 1 Compositions for Samples 1-4 Sample 1 Sample 2 Sample 3 Sample 4Cyclohexanedimethanol 100 mole % 31 mole % 31 mole % 31 mole % EthyleneGlycol 0 mole % 69 mole % 69 mole % 69 mole % Terephthalic Acid 52 mole% 100 mole % 100 mole % 100 mole % Isophthalic Acid 48 mole % 0 mole % 0mole % 0 mole %

Some of the characteristics of the samples were measured according toASTM D standards. The results of the sample measurements are shown inTable 2.

TABLE 2 Physical Property Measurements for Samples 1-4 Sample 1 Sample 2Sample 3 Sample 4 Density (g/cm³) 1.20 1.28 1.28 1.27 Inherent Viscosity(dL/g) 0.64 0.59 0.75 0.75 Glass Transition 84 78 78 78 Temperature (°C.) Crystallization 128 >1500 >1500 >1500 Half-Time (minutes) Zero Shear2750 2810 — — Viscosity (Poise) Heat Deflection 63 62 62 62 Temperature(° C.) Tensile Strength 50 51 51 50 at Yield (MPa) Elongation at Break(%) 193 33 33 110 Flexural Modulus (MPa) 1814 2007 2007 2100 NotchedIzod Impact 70 69 98 95 Strength (J/m)

The density of the samples was measured using the ASTM D 792 standard atthe time of filing of this patent application. In addition, the inherentviscosity of the samples was measured in approximately a 60/40 solutionof phenol/tetrachloroethane at a concentration of about 0.5 g/100 ml atabout 25° C. In addition, the glass transition temperature of thesamples was measured using a TA Instruments differential scanningcalorimeter (DSC) at a scan rate of about 20° C.

The crystallization half-time of the samples was measured using a smallangle light scattering (SALS) technique with a helium-neon laser. Inparticular, the sample was melted at about 280° C. to remove preexistingcrystallinity. The sample was then rapidly cooled to a predeterminedcrystallization temperature from about 140° C. to about 160° C. and thetransmitted light intensity was recorded as a function of time. The timeat which the light intensity drops to half the original value denotesthe crystallization half-time.

The zero shear viscosity of the samples was measured using smallamplitude oscillatory shear (SAOS) rheology conducted with RDA II fromRheometrics Scientific. A frequency sweep from about 1 to about 400rad/s was performed at about 260° C. using about a 10% strain value. Thesamples exhibited a Newtonian-like plateau in the 1-10 rad/s shear rateregime. The viscosity measured at about 1 rad/s was reported as thezero-shear viscosity.

For the remaining tests, an ASTM test bar was molded on a Toyo 90injection molding machine. The pellets of the samples were first driedat about 70° C. for about 3-6 hours. The molding melt temperature wasabout 260° C. and the mold temperature was about 30° C. The heatdeflection temperature of the samples was measured at about 264 psiaccording to the ASTM D 648 standard at the time of filing this patentapplication. In addition, the flexural modulus was measured according tothe ASTM D 790 standard at the time of filing this patent application.Further, the tensile strength at yield and the elongation at break weremeasured according to the ASTM D 638 standard at the time of filing ofthis patent application. Also, the notched Izod impact strength of thesamples were measured at about 23° C. according to the ASTM D 256standard at the time of filing of this patent application.

Example 2

Objects were produced using filaments formed from samples 1-4 of Table 1and inherent viscosity of the objects was measured in approximately a60/40 solution of phenol/tetrachloroethane at a concentration of about0.5 g/100 ml. The solution was heated to about 150° C. to mix anddissolve the material in the solution. The solution was then cooled toabout 25° C. The inherent viscosity was determined by measuring thepressure used to force the solution down a narrow bore stainless steeltube relative to the pressure used to force the 60/40phenol/tetrachloroethane solution without the material down the tube.

Table 3 shows the process conditions and inherent viscosity (I.V.)measurements for objects made from filaments of polymeric materialscorresponding to samples 1-4 of Table 1 with the extrusion head having afirst rate of extrusion of about 7.6 mm³/s for sample 1, about 7.4 mm³/sfor sample 2, about 4.4 mm³/s for sample 3, and about 4 mm³/s for sample4. Table 4 shows the process conditions and inherent viscositymeasurements for objects made from filaments of polymeric materialscorresponding to samples 1-4 of Table 1 with the extrusion head having asecond rate of extrusion of about 8.7 mm³/s for sample 1, about 8.8mm³/s for sample 2, about 4.8 mm³/s for sample 3, and about 4.1 mm³/sfor sample 4. The inherent viscosity loss was calculated in Tables 3 and4 based on a first inherent viscosity of the polymeric material beforethe objects were produced and a second inherent viscosity of thecompleted objects. The first inherent viscosity for sample 1 was about0.619 dL/g, the first inherent viscosity for sample 2 was about 0.588dL/g, the first inherent viscosity for sample 3 was about 0.720 dL/g,and the first inherent viscosity for sample 4 was about 0.735 dL/g. Thesecond inherent viscosity measurements of the completed objects areshown in Tables 3 and 4.

TABLE 3 Inherent viscosity and inherent viscosity loss for objectsproduced using additive manufacturing at a first rate of extrusion.Sample 1 Sample 2 Sample 3 Sample 4 I.V. I.V. I.V. I.V. (dL/g)/ (dL/g)/(dL/g)/ (dL/g)/ Temp. I.V. I.V. I.V. I.V. (° C.) Loss (%) Loss (%) Loss(%) Loss (%) 220 0.612/1 0.572/3 0.676/6  0.689/6  225 0.611/1 0.562/40.672/7  0.668/9  230 0.611/1 0.555 6 0.651/10 0.662/10 235 0.606/20.552/6 0.632/12 0.631/14 240 0.606/2 0.554/6 0.619/14 0.618/16 2450.604/2 0.549/7 0.613/15 0.602/18 250 0.601/3 0.544/7 0.607/16 0.602/18255 0.599/4 0.538/9 0.605/16 0.596/19 260 0.599/4 0.543/8 0.597/170.592/19

TABLE 4 Inherent viscosity and inherent viscosity loss for objectsproduced using additive manufacturing at a second rate of extrusion.Sample 1 Sample 2 Sample 3 Sample 4 I.V. I.V. I.V. I.V. (dL/g)/ (dL/g)/(dL/g)/ (dL/g)/ Temp. I.V. I.V. I.V. I.V. (° C.) Loss (%) Loss (%) Loss(%) Loss (%) 220 0.616/0 0.581/1 0.708/2 0.712/3 225 0.616/0 0.573/30.698/3 0.711/3 230 0.618/0 0.572 3 0.686/5 0.698/5 235 0.613/1 0.567/40.676/6 0.692/6 240 0.612/1 0.563/4 0.666/7 0.676/8 245 0.610/1 0.556/50.657/9  0.660/10 250 0.602/3 0.551/6  0.637/12  0.649/13 255 0.601/30.551/6  0.622/14  0.619/16 260 0.604/4 0.552/6  0.610/15  0.608/17

Table 5 shows a summary of process conditions and inherent viscositychange between the inherent viscosity of a polymeric material beforebeing used to produce an object using extrusion-based additivemanufacturing and the inherent viscosity of a completed object producedfrom the polymeric material. The maximum temperature and the minimumtemperature of Table 5 indicate the maximum and minimum temperatures atwhich adhesion between the layers of the object are sufficient. Theobjects produced from the polymeric material of sample 1 had values forthe inherent viscosity drop that were less than that of objects producedusing polymeric materials of samples 2-4. Additionally, the temperaturerange at which the objects produced using the polymeric material ofsample 1 was greater than that of objects produced using polymericmaterials of samples 2-4.

TABLE 5 Process conditions and inherent viscosity change between theinherent viscosity of a polymeric material before being used to producean object and the inherent viscosity of a completed object produced fromthe polymeric material. Temp. (° C.) Rate (mm³/s) I.V. Drop Min MaxDelta (° C.) Min Max Min Max Sample 1 230 245 15 7.6 8.7 0%  2% Sample 2225 235 10 7.4 8.8 3%  7% Sample 3 235 245 10 4.4 4.8 6% 14% Sample 4235 245 10 4 4.1 6% 18%

Adhesion was tested by using an Ultimaker 2 extrusion based additivemanufacturing system to produce layers of objects at differenttemperatures while holding the speed relatively constant. A Pythonscript was used to direct the system to form the layers of the objects.The adhesion was then tested at the different temperatures through amanual test of the amount of force exerted by a human hand to separatethe layers. The minimum and maximum temperatures shown in Table 5 wererecorded when the layers could not be readily separated by the use of ahuman hand.

FIG. 5 shows an example object produced at an extrusion rate of about 1mm³/s where the filament is heated at different temperatures beforeextruding the filament to form the object. In particular, the objectshown in FIG. 5 is produced from a polymeric material according to thecomposition of Sample 4. When a different temperature was used to heatthe filament prior to extrusion, a layer having a diameter that was lessthan the diameter of a previously formed layer was produced to aid indemarcating the transition between temperatures. The object shown inFIG. 5 includes demarcation lines indicating layers formed at 220° C.,225° C., 230° C., 235° C., and 240° C. FIG. 5 also shows that visualdegradation of the object takes place when the layers of the object areproduced at temperatures above 240° C. As the object shown in FIG. 5 wasproduced, adhesion was tested at each temperature transition point. Forexample, adhesion between the layers produced at 220° C. and adhesionbetween layers produced at 225° C. was tested by trying to separate therespective layers at the ring indicated in FIG. 5. Subsequent tests wereperformed for each of the temperature transitions. The same procedurewas followed to test adhesion between layers produced at differenttemperatures for polymeric materials having compositions correspondingto Sample 1, Sample 2, and Sample 3. FIG. 6 shows an object producedusing a polymeric material having a composition corresponding to Sample1 at an extrusion rate of about 2 mm³/s, where the filament is heated atdifferent temperatures before extruding the filament to form the object.FIG. 6 shows that visual degradation of the object occurs attemperatures above 245° C. Table 6 shows visual degradation temperaturesfor objects produced using compositions of Sample, 1, Sample 2, Sample3, and Sample 4. The first extrusion rate measurements are taken at arate of extrusion of about 1 mm³/s and the second extrusion ratemeasurements are taken at a rate of extrusion of about 2 mm³/s.

TABLE 6 Temperatures at which visual degradation is observed in ° C.First Extrusion Second Extrusion Rate Rate Sample 1 245 260 Sample 2 235250 Sample 3 245 260 Sample 4 245 265

FIG. 7 shows an object produced using the composition of Sample 4 at atemperature of about 235° C. using an extrusion based additivemanufacturing apparatus. The extrusion rate at which the layers of theobject were formed increased with increasing height of the object.Additionally, FIG. 8 shows an object produced using the composition ofSample 1 at a temperature of about 235° C. using an extrusion basedadditive manufacturing apparatus, where the extrusion rate at which thelayers of the object were formed increased with increasing height of theobject. The initial extrusion rate was about 1 mm³/s. The extrusionrates recorded in Table 5 were calculated by measuring a height of anobject formed according to the composition corresponding to therespective sample before degradation occurred using the followingformula:

${{Extrusion}\mspace{14mu} {Rate}\mspace{14mu} {in}\mspace{14mu} {mm}^{3}\text{/}s} = {\frac{{height}\mspace{14mu} {measured}}{5} + {{initial}\mspace{14mu} {extrusion}\mspace{14mu} {rate}}}$

The constant “5” in the formula indicates that the extrusion rateincreases by 1 mm³/s for every 5 mm of the object produced. The heightof the tower shown in FIG. 8 versus the height of the tower shown inFIG. 7 shows that the polymeric material used to produce the tower ofFIG. 8 can be used to form objects over a greater range of extrusionrates indicating physical properties that are more conducive toextrusion-based additive manufacturing processes than the polymericmaterial used to form the tower of FIG. 7.

Notched Izod testing was performed on objects produced from polymericmaterials related to samples 1-4 and the results are shown in Table 7.The highest and lowest values in Table 6 for the notched Izod testresults are measured in KJ/m². The notched Izod tests were carried outaccording to the ASTM D256 standard at the time of filing of this patentapplication. The objects produced from the polymeric materialcorresponding to sample 1 had the least variability in the notched Izodtest results.

TABLE 7 Notched Izod test results. Max Min Delta Variability Sample 1 4746.5 0.5 0.03 Sample 2 47.3 46.7 0.6 0.06 Sample 3 47.4 46.4 1 0.1Sample 4 47.9 45.7 2.2 0.22

Conclusion

In closing, although the various implementations have been described inlanguage specific to structural features and/or methodological acts, itis to be understood that the subject matter defined in the appendedrepresentations is not necessarily limited to the specific features oracts described. Rather, the specific features and acts are disclosed asexample forms of implementing the claimed subject matter.

ILLUSTRATIVE EXAMPLES OF INVENTIVE CONCEPTS

While Applicant's disclosure includes reference to specificimplementations above, it will be understood that modifications andalterations may be made by those practiced in the art without departingfrom the spirit and scope of the inventive concepts described herein.All such modifications and alterations are intended to be covered. Assuch the illustrative examples of the inventive concepts listed beloware merely illustrative and not limiting.

Example 1

An article comprising: a plurality of layers of a polymeric materialthat includes units of a diacid component and units of a glycolcomponent, wherein the units of the diacid component are derived from afirst diacid and a second diacid.

Example 2

The article of example 1, wherein the plurality of layers are arrangedaccording to a design.

Example 3

The article of any one of examples 1-2, wherein the first diacid isterephthalic acid and the second diacid is isophthalic acid, acyclohexanedicarboxylic acid, a naphthalenedicarboxylic acid, astilbenedicarboxylic acid, or a combination thereof.

Example 4

The article of any one of examples 1-3, wherein the diacid componentincludes from about 40 mole % to about 60 mole % of units derived fromthe first diacid and from about 40 mole % to about 60 mole % of unitsderived from the second diacid.

Example 5

The article of any one of examples 1-3, wherein the diacid componentincludes from about 45 mole % to about 55 mole % of units derived fromterephthalic acid and from about 45 mole % to about 55 mole % of unitsderived from isophthalic acid.

Example 6

The article of any one of examples 1-5, wherein the units of the glycolcomponent are derived from cyclohexanedimethanol.

Example 7

The article of any one of examples 1-6, wherein the glycol componentincludes from about 75 mole % to about 98 mole % of units derived from afirst glycol and from about 2 mole % to about 25 mole % of units derivedfrom one or more second glycols.

Example 8

The article of example 7, wherein the first glycol includescyclohexanedimethanol and the one or more second glycols includeethylene glycol, a propanediol, neopentyl glycol, a butanediol, apentanediol, a hexanediol, p-xylene glycol, or a combination thereof.

Example 9

The article of any one of examples 1-8, wherein the polymeric materialhas an inherent viscosity from about 0.55 dig to about 0.7 dig, adensity no greater than about 1.25 g/cm3, a glass transition temperatureof at least about 80° C., and a crystallization half-time no greaterthan about 300 minutes.

Example 10

An article comprising: a body comprised of a polymeric material thatincludes units of a diacid component and units of a glycol component,wherein: the body has a diameter from about 1 mm to about 5 mm and alength of at least about 3 cm; and an inherent viscosity loss of anobject formed from the polymeric material relative to the polymericmaterial before forming the object is no greater than about 0.9%.

Example 11

The article of example 10, wherein the polymeric material has a zeroshear viscosity no greater than about 3000 Poise.

Example 12

The article of any one of examples 10-11, wherein the polymeric materialhas an elongation at break of at least about 75%.

Example 13

The article of any one of examples 10-12, wherein the polymeric materialhas a density no greater than about 1.25 g/cm3.

Example 14

The article of any one of examples 10-13, wherein the polymeric materialhas a glass transition temperature of at least about 80° C.

Example 15

The article of any one of examples 10-14, wherein the body has a lengthof at least about 3 cm.

Example 16

The article of any one of examples 10-15, wherein the body has adiameter from about 1.5 mm to about 3 mm and a length of at least about2 m.

Example 17

The article of any one of examples 10-16, wherein the units of theglycol component are derived from cyclohexanedimethanol, from about 40mole % to about 60 mole % of the units of the diacid component arederived from terephthalic acid, and from about 40 mole % to about 60mole % of the units of the diacid component are derived from isophthalicacid.

Example 18

A process comprising: heating a polymeric material at a temperature fromabout 225° C. to about 250° C., the polymeric material including unitsof a diacid component and units of a glycol component; extruding aplurality of layers of the polymeric material onto a substrate to forman object, where a rate of extrusion is from about 7 mm³/s to about 9mm³/s; wherein an inherent viscosity loss of the object relative to thepolymeric material before forming the object is no greater than about 5%when the polymeric material is heated at a temperature of about 250° C.

Example 19

The process of example 18, wherein the plurality of layers of thepolymeric material are deposited onto the substrate according to apredetermined design.

Example 20

The process of any one of examples 18-19, wherein depositing theplurality of layers of the polymeric material onto the substrateincludes extruding the polymeric material onto the substrate via anextrusion head.

Example 21

The process of any one of examples 18-20, wherein the units of theglycol component are derived from cyclohexanedimethanol, from about 40mole % to about 60 mole % of the units of the diacid component arederived from terephthalic acid, and from about 40 mole % to about 60mole % of the units of the diacid component are derived from isophthalicacid.

Example 22

The process of any one of examples 17-21, wherein the polymeric materialhas an inherent viscosity from about 0.55 dig to about 0.7 dig, adensity no greater than about 1.25 g/cm3, a glass transition temperatureof at least about 80° C., and a crystallization half-time no greaterthan about 300 minutes.

Example 23

The process of any one of examples 17-22, wherein the inherent viscosityloss is no greater than about 2%.

Example 24

A process comprising: combining a diacid component and a glycolcomponent to form a polymeric material, wherein the diacid componentincludes a first diacid and a second diacid; extruding the polymericmaterial to form a filament, the filament having a body with a diameterfrom about 1 mm to about 5 mm and a length of at least about 3 cm.

Example 25

The process of example 24, wherein the extruding the polymeric materialto form the filament is performed by an extruder having a single screwor a twin screw.

Example 26

The process of example 25, wherein a screw speed of the extruder is fromabout 60 rotations per minute (rpm) to about 85 rpm.

Example 27

The process of example 25, wherein at least one chamber of the extruderis heated at a temperature from about 210° C. to about 240° C.

Example 28

The process of any one of examples 24-27, further comprising grindingpellets of at least one of the diacid component or the glycol componentbefore combining the diacid component and the glycol component.

Example 29

The process of any one of examples 24-28, wherein the filament has alength of at least about 30 cm.

Example 30

The process of any one of examples 24-29, wherein the filament has alength from about 30 cm to about 5 m.

Example 31

The process of any one of examples 24-30, further comprising: depositinga plurality of layers of the filament onto a substrate according to apredetermined design to produce an object; and removing the object fromthe substrate.

Example 32

The process of any one of examples 24-31, wherein the units of theglycol component are derived from cyclohexanedimethanol and the units ofthe diacid component are derived from terephthalic acid and isophthalicacid.

1. An article comprising: a plurality of layers of a polymeric materialthat includes units of a diacid component and units of a glycolcomponent, wherein the units of the diacid component are derived from afirst diacid and a second diacid.
 2. The article of claim 1, wherein theplurality of layers are arranged according to a design.
 3. The articleof claim 1, wherein the first diacid is terephthalic acid and the seconddiacid is isophthalic acid, a cyclohexanedicarboxylic acid, anaphthalenedicarboxylic acid, a stilbenedicarboxylic acid, or acombination thereof.
 4. The article of claim 1, wherein the diacidcomponent includes from about 40 mole % to about 60 mole % of unitsderived from the first diacid and from about 40 mole % to about 60 mole% of units derived from the second diacid.
 5. The article of claim 1,wherein the diacid component includes from about 45 mole % to about 55mole % of units derived from terephthalic acid and from about 45 mole %to about 55 mole % of units derived from isophthalic acid.
 6. Thearticle of claim 1, wherein the units of the glycol component arederived from cyclohexanedimethanol.
 7. The article of claim 1, whereinthe glycol component includes from about 75 mole % to about 98 mole % ofunits derived from a first glycol and from about 2 mole % to about 25mole % of units derived from one or more second glycols.
 8. The articleof claim 7, wherein the first glycol includes cyclohexanedimethanol andthe one or more second glycols include ethylene glycol, a propanediol,neopentyl glycol, a butanediol, a pentanediol, a hexanediol, p-xyleneglycol, or a combination thereof.
 9. The article of claim 8, wherein thepolymeric material has an inherent viscosity from about 0.55 dL/g toabout 0.7 dL/g, a density no greater than about 1.25 g/cm³, a glasstransition temperature of at least about 80° C., and a crystallizationhalf-time no greater than about 300 minutes.
 10. An article comprised offused filament polymer layers arranged in a design, said polymercomprising a polyester having an acid component and a glycol component;wherein the acid component comprises repeat units from 30 to 70 mole %terephthalic acid and from 70 to 30 mole % of one or more dibasic acidsselected from the group consisting of isophthalic acid,1,3-cyclohexanedicarboxylic acid, 1,4 cyclohexanedicarboxylic acid,1,4-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid,2,6-naphthalenedicarboxylic acid, or 2,7-naphthalenedicarboxylic acid,stilbenedicarboxylic acid, sebacic acid, dimethylmalonic acid, succinicacid, or combinations thereof; wherein the glycol component comprisesrepeat units from 75 to 98 mole % cyclohexanedimethanol and from 2 to 25mole % glycols selected from the group consisting of ethylene glycol,1,2-propanediol, 1,3-propanediol, neopentyl glycol, 1,4-butanediol,1,5-pentanediol, 1,6-hexanediol, p-xylene glycol,2,2,4,4-tetramethyl-1,3-cyclobutanediol or combinations thereof; whereinthe total mole % of the acid component is 100 mole % and the total mole% of the glycol component in 100 mole %; wherein the polyester has aninherent viscosity of 0.55 dL/g to 0.7 dL/g, a density no greater thanabout 1.35 g/cm³, a glass transition temperature of 70° C. to 110° C.,an elongation at break of at least about 75%, a zero shear viscosity of1750 to 8000 poise and a crystallization half-time no greater than about300 minutes.
 11. The article of claim 10, wherein the diacid componentincludes from 45 mole % to 55 mole % of units derived from terephthalicacid and from 45 mole % to 55 mole % of units derived from isophthalicacid.
 12. The article of claim 10 wherein the acid component furthercomprises 0.1 mole % to 1.5 mole % of a branching agent selected fromthe group consisting of trimellitic anhydride, trimellitic acid,pyromellitic dianhydride, trimesic acid, hemimellitic acid, glycerol,trimethylolpropane, pentaerythritol, 1,2,4-butanetriol,1,2,6-hexanetriol, sorbitol, 1,1,4,4-tetrakis(hydroxymethy)cyclohexane,dipentaerythritol, or combinations thereof.